Effects of drip irrigation on root activity pattern, root-sourced signal characteristics and yield stability of winter wheat

A field experiment was conducted to explore the mechanism of drip fertilization to increase grain yield and water productivity (WP) of winter wheat. The traditional irrigation and fertilization method (surface flooding irrigation + artificially applying fertilizer) was used as CK, and two drip fertilization methods were set up: surface drip fertilization (I1) and subsurface drip fertilization (I2). The results showed that drip fertilization affected the root morphological pattern (RMP) and root activity pattern (RAP)of wheat by affecting the distribution of water and nitrogen in the soil. At heading stage, both I1 and I2 had higher root weight density (RWD) and root length density (RLD) in deep soil layer (40–80 cm) compared with CK, but lower RWD and RLD in the topsoil layer (0–20 cm). I1 and I2 had greater root activity in deep soil layer compare to CK, but root activity of I2 in 0–20 cm surface soil was lower than that of CK and I1. Drip fertilization also affected the distribution space of maximum root activity (MRA) of plant. At heading stage, the distribution space of MRA of I1 and I2 was the same as that of CK, and all of them were located in 20–40 cm soil layer. At the filling stage, MRA of CK was located in 40–80 cm soil layer, and that of I1 and I2 were in 20–60 cm soil layer. Plant can adjust its water uptake strategy and RAP according to soil moisture and the growth stages. Plants in I1 and CK mainly use water from 0 to 20 cm soil layer at jointing stage (one week after irrigation), and I2 mainly absorbs water from 20 to 40 cm soil layer. At the filling stage (three weeks after irrigation), the main uptake space (MUS) of root moved to 40–80 cm soil layers, but I1 and I2 had greater water uptake capacity in this position compared with CK. Drip fertilization also triggered non-hydraulic root-sourced signal (nHRS) earlier, but delayed the emergence of hydraulic root-sourced signal (HRS). In addition, the grain yield, yield stability (YS) and WP of I1 and I2 were higher than those of CK. In conclusion, drip fertilization optimized RMP, RAP and root-sourced signal characteristics of crop by improving the water and fertilizer environment in the root zone, thus improving grain yield, YS and WP of crop.